Operations of Attach/Detach in a mobile communication system will be described with reference to FIG. 8. Further, operations in the case of an outgoing call/an incoming call in the mobile communication system will be described with reference to FIG. 9. Attach is the processing to register the location of a mobile station apparatus such as a portable telephone or the like to a network. Typically, Attach is executed when a power supply of the mobile station apparatus is turned on or when the mobile station apparatus moves between cells. Detach is the processing to cancel the location registration of the mobile station apparatus to the network. Typically, Detach is executed when a power supply of the mobile station apparatus is turned off.
In FIG. 8, after Power ON (S500), a mobile station 100 reads out USIM (Universal Subscriber Identity Module) information stored in the mobile station 100 (S501). Then, the mobile station 100 executes Attach procedure based on the USIM information among the mobile station 100, a radio base station 120, and a CN (core network) 130 (S502). Then, the mobile station 100 displays a standby screen (S503). After a predetermined period of time, the mobile station 100 executes Detach procedure among the mobile station 100, the radio base station 120, and the CN 130 (S504). However, at this time, the mobile station 100 does not delete the USIM information.
Further, in FIG. 9, when the mobile station 100 performs an outgoing call or an incoming call (S601) from the state in which the standby screen is displayed (S600), the mobile station 100 reads out user information stored therein (S602). The mobile station 100 then stores the history in the mobile 100 station (S603). Then, the mobile station 100 executes the procedure of the outgoing call or the incoming call (S604), to connect with the radio base station 120 and the CN 130 (S605). After executing the call end procedure (S606), the mobile station 100 displays the standby screen without deleting the user information (S607).
According to the mobile communication system stated above, when the user loses the mobile station apparatus and the mobile station apparatus is passed into the hands of a third party, the user information that remains inside the mobile station apparatus may be known to the third party. In order to address this problem, Patent literature 1 suggests, for example, a mobile radio telephone system that remotely deletes user information of a mobile station in the range of radio communication when the user finds that the mobile station apparatus is lost. In the mobile radio telephone system disclosed in Patent literature 1, when the base station checks the location registration of the mobile station, the base station sends a user information transmission signal to the mobile station, and the mobile station that receives the signal deletes the user information stored therein after transmitting this information to the base station.